Field of the Invention
Certain embodiments of the present invention generally relate to simultaneous peer-to-peer circuit switched and Internet protocol multimedia subsystem communication.
Description of the Related Art
With the deployment of support for conversational Internet protocol multimedia subsystem (IMS) in the packet switched (PS) domain, a network operator may have the potential to support conversational services in the circuit switched (CS) domains. In the early days of the deployment of conversational PS services, the probability of an entire network supporting conversational PS services was low. However, when a user equipment (UE) initiates a conversational service in the PS domain, there is a high probability that it will fail. Failure would require the US to re-request the service on the PS domain. This can introduce an unacceptable and substantial delay in the call setup time. To allow a good user experience in terms of call setup time and to reduce the unnecessary signaling traffic, the UE should operate in the CS domain for conversational services.
Once the deployment of conversational PS services has progressed in many markets, the probability of a conversational service being supported by the PS domain will be much greater. As operator and handset manufacturer might generally want the UE to operate in the PS domain as much as possible to allow the user to maximize the advanced functionality of the handset, thus allowing differentiation of the handset and network.
It is important for the UE to know this to be able to select the proper domain (PS or CS) when establishing a conversational multimedia session. It is also important for the IMS to know this to be able to select the proper domain (PS or CS) when a UE terminated conversational multimedia session is established.
CS & IMS combinational services (CSICS) are being specified in the Third Generation Partnership Project (3GPP) Release 7. The basic concept in the specification is that a CSICS capable UE can have simultaneous peer-to-peer CS and IMS communication, and present it within one context to the user. To achieve this, the communicating UEs generally indicate their CSICS capabilities to each other and are aware of the capabilities of the radio access network, i.e. whether the network supports simultaneous CS and PS services. A capability exchange procedure, based on the exchange of session initiation protocol (SIP) messages, is applied between the communicating UEs.
However, a challenge actively being discussed in 3GPP standardization is how the UE and the IMS network know whether a conversational Quality of Service (QoS) is supported between the UE and the IMS, i.e., conversational QoS supported by the UE, by the radio access network, and by the IMS network.